Constraining angular momentum transport processes in stellar interiors with red-giant stars in the open cluster NGC6819

Clusters are excellent test benches for verification and improvement of stellar evolution theory. The recent detection of solar-like oscillations in G-K giants in the open cluster NGC6819 with Kepler provides us with independent constraints on the masses and radii of stars on the red giant branch, as well as on the distance to clusters and their ages. We present, for NGC6819, evolutionary models by considering rotation-induced mixing ; and the theoretical low-l frequencies of our stellar models.Comment: Submitted to EPJ Web of Conferences, to appear in the Proceedings of the 3rd CoRoT Symposium, Kepler KASC7 joint meeting; 2 pages, 1 figur

Mucopolysaccharidosis type III: an updated review

El objetivo de este trabajo es revisar la literatura científica acerca de la mucopolisacaridosis tipo III con el fin de describir sus características principales. Así, se delimita el cuadro clínico y los fenotipos que se consideran a la hora de estudiar este síndrome. A continuación se analizan las pruebas bioquímicas que se llevan a cabo para el diagnóstico específico de esta patología. Posteriormente se revisan puntos clave del diagnóstico precoz y las pruebas actuales que permiten realizar el diagnóstico prenatal y las pruebas genéticas. Igualmente se establece el papel del pediatra y del médico de atención primaria como pilares principales en el seguimiento del paciente así como la importancia de otros especialistas en función de las necesidades de este. Por último, se describen las opciones de tratamiento existentes en el momento actual y las terapias en vías experimentales de mayor relevancia. De este modo, evaluaremos los puntos más importantes de la enfermedad, a fin de facilitar no solo la comprensión de la misma, sino también procurando que el lector conozca el reto que supone esta patología para la medicina en la actualidad.This paper is aimed at revising the scientific literature about mucopolysaccharidosis type III in order to describe its main features. Firstly, the clinical presentation as well as the different phenotypes included in this syndrome are explained. Secondly, biochemical exams used in the specific diagnosis of this syndrome are reviewed. Also, key points related to early diagnosis, prenatal and genetics testings are highlighted. The role of pediatricians and primary care physicians as main actors in the patients’ follow-up and the importance of other specialists depending on the patients’ needs are assessed. Finally, current treatment options and experimental studies for new therapies are described. The most relevant aspects of MPS III are reviewed, facilitating the comprehension of this disease and thus making the readers aware of this challenge in medicine nowadays

NGC 6819: testing the asteroseismic mass scale, mass loss, and evidence for products of non-standard evolution

We present an extensive peakbagging effort on Kepler data of $\sim$50 red giant stars in the open star cluster NGC 6819. By employing sophisticated pre-processing of the time series and Markov Chain Monte Carlo techniques we extracted individual frequencies, heights and linewidths for hundreds of oscillation modes. We show that the "average" asteroseismic parameter $\delta\nu_{02}$, derived from these, can be used to distinguish the stellar evolutionary state between the red giant branch (RGB) stars and red clump (RC) stars. Masses and radii are estimated using asteroseismic scaling relations, both empirically corrected to obtain self-consistency as well as agreement with independent measures of distance, and using updated theoretical corrections. Remarkable agreement is found, allowing the evolutionary state of the giants to be determined exclusively from the empirical correction to the scaling relations. We find a mean mass of the RGB stars and RC stars in NGC 6819 to be $1.61\pm0.02\,\textrm{M}_\odot$ and $1.64{\pm}0.02\,\textrm{M}_\odot$, respectively. The difference $\Delta M=-0.03\pm0.01\,\textrm{M}_\odot$ is almost insensitive to systematics, suggesting very little RGB mass loss, if any. Stars that are outliers relative to the ensemble reveal overmassive members that likely evolved via mass-transfer in a blue straggler phase. We suggest that KIC 4937011, a low-mass Li-rich giant, is a cluster member in the RC phase that experienced very high mass-loss during its evolution. Such over- and undermassive stars need to be considered when studying field giants, since the true age of such stars cannot be known and there is currently no way to distinguish them from normal stars.Comment: 21 pages, 11 figure

Los e-pacientes en Oncología: caracterización basada en corpus de la terminología médica en un foro en línea sobre cáncer

This study aimed to characterize medical terms in an online cancer forum, with particular focus on specialization and semantic features. A three-step analysis was carried out on a 60-million-word corpus to detect and characterize the most typical medical terms used in a cancer forum by means of (1) keywords contrastive, (2) co-text-guided, and (3) semantic analyses. More than half of the 1000 words analysed were medical terms according to the co-text-guided analysis carried out. Most of them (73%) were dictionary-defined medical terms, followed by co-text-defined terms (9%) and medical initialisms (8.5%). The semantic analysis showed a higher number of terms within the fields of Anatomy, Treatment, Hospital and Symptoms. Our findings suggest that medical terms are commonly used in cancer forums, especially to share e-patients’ concerns about treatment, symptoms and hospital environment. The method followed is efficient and could be applied in future studies. Altogether, this article contributes to characterizing medical terms used by e-patients in online cancer forums.El objetivo de este estudio fue caracterizar los términos médicos de un foro en línea sobre cáncer, prestando especial atención a los rasgos semánticos y de especialización. Con el fin de detectar y caracterizar los términos médicos más típicos utilizados en un foro de cáncer, se llevó a cabo un análisis de un corpus de 60 millones de palabras en tres etapas: (a) contraste de palabras clave, (b) estudio del cotexto y (c) análisis semántico. Más de la mitad de las 1000 palabras analizadas eran términos médicos de acuerdo con el análisis guiado por el contexto. La mayor parte de ellas (el 73%) se corresponden con “términos médicos definidos en el diccionario”, seguidos de “términos definidos por el cotexto” (9%) y de “siglas y abreviaturas médicas” (8,5%). En el análisis semántico se encontró un mayor número de términos en los campos de Anatomía, Tratamiento, Hospital y Síntomas. Nuestros hallazgos sugieren que los términos médicos son frecuentemente utilizados en los foros oncológicos, sobre todo para compartir las preocupaciones de los e-pacientes sobre el tratamiento, los síntomas y el medio hospitalario. El método seguido es eficiente y podría aplicarse en estudios futuros. En definitiva, este artículo contribuye a la caracterización de los términos médicos utilizados por los e-pacientes en foros en línea sobre cáncer

The extended halo of NGC 2682 (M 67) from Gaia DR2

Context: NGC 2682 is a nearby open cluster, approximately 3.5 Gyr old. Dynamically, most open clusters should dissolve on shorter timescales, of ~ 1 Gyr. Having survived until now, NGC 2682 was likely much more massive in the past, and is bound to have an interesting dynamical history. Aims: We investigate the spatial distribution of NGC 2682 stars to constrain its dynamical evolution, especially focusing on the marginally bound stars in the cluster outskirts. Methods: We use Gaia DR2 data to identify NGC 2682 members up to a distance of ~150 pc (10 degrees). Two methods (Clusterix and UPMASK) are applied to this end. We estimate distances to obtain three-dimensional stellar positions using a Bayesian approach to parallax inversion, with an appropriate prior for star clusters. We calculate the orbit of NGC 2682 using the GRAVPOT16 software. Results: The cluster extends up to 200 arcmin (50 pc) which implies that its size is at least twice as previously believed. This exceeds the cluster Hill sphere based on the Galactic potential at the distance of NGC 2682. Conclusions: The extra-tidal stars in NGC 2682 may originate from external perturbations such as disk shocking or dynamical evaporation from two-body relaxation. The former origin is plausible given the orbit of NGC 2682, which crossed the Galactic disk ~40 Myr ago.Comment: 9 pages, 5 figures, accepted for publication on A&

Laser-driven quantum magnonics and THz dynamics of the order parameter in antiferromagnets

The impulsive generation of two-magnon modes in antiferromagnets by femtosecond optical pulses, so-called femto-nanomagnons, leads to coherent longitudinal oscillations of the antiferromagnetic order parameter that cannot be described by a thermodynamic Landau-Lifshitz approach. We argue that this dynamics is triggered as a result of a laser-induced modification of the exchange interaction. In order to describe the oscillations we have formulated a quantum mechanical description in terms of magnon pair operators and coherent states. Such an approach allowed us to} derive an effective macroscopic equation of motion for the temporal evolution of the antiferromagnetic order parameter. An implication of the latter is that the photo-induced spin dynamics represents a macroscopic entanglement of pairs of magnons with femtosecond period and nanometer wavelength. By performing magneto-optical pump-probe experiments with 10 femtosecond resolution in the cubic KNiF$_3$ and the uniaxial K$_2$NiF$_4$ collinear Heisenberg antiferromagnets, we observed coherent oscillations at the frequency of 22 THz and 16 THz, respectively. The detected frequencies as a function of the temperature ideally fit the two-magnon excitation up to the N\'eel point. The experimental signals are described as dynamics of magnetic linear dichroism due to longitudinal oscillations of the antiferromagnetic vector.Comment: 25 pages, 10 figure

Exchange-mediated magnetic blue-shift of the band-gap energy in the antiferromagnetic semiconductor MnTe

In magnetic semiconductors the optical spectrum and, in particular, the absorption edge representing the band-gap are strongly affected by the onset of the magnetic order. This contribution to the band-gap energy has hitherto been described theoretically in terms of a Heisenberg Hamiltonian, in which a delocalized conduction carrier is coupled to the localized magnetic moments by the exchange interaction. Such models, however, do not take into account the strong correlations displayed in a wide variety of magnetic semiconductors, which are responsible for the formation of the local moments. In particular, the itinerant carrier itself contributes to the spin moment. Here, we overcome this simplification in a combined experimental and theoretical study of the antiferromagnetic semiconductor α-MnTe. First, we present a spectroscopic optical investigation as a function of temperature, from which we extract the magnetic contribution to the blue-shift of the band-gap. Second, we formulate a minimal model based on a Hubbard–Kondo Hamiltonian. In this model, the itinerant charge is one of the electrons forming the localized magnetic moment, which properly captures correlation effects in the material. Our theory reproduces the experimental findings with excellent quantitative agreement, demonstrating that the magnetic contribution to the band-gap energy of α-MnTe is mediated solely by the exchange interaction. These results describe an intrinsic property of the material, independent of the thickness, substrate and capping layer of the specimen. One of the key findings of the model is that the basic effect, namely a blue-shift of the band-gap due to the establishment of the magnetic order, is a general phenomenon in charge-transfer insulators. The identification of the relevant magnetic interaction discloses the possibility to exploit the effect here discussed to induce a novel regime of coherent spin dynamics, in which spin oscillations on a characteristic time-scale of 100 fs are triggered and are intrinsically coupled to charges

Macrospin dynamics in antiferromagnets triggered by sub-20 femtosecond injection of nanomagnons

The understanding of how the sub-nanoscale exchange interaction evolves in macroscale correlations and ordered phases of matter, such as magnetism and superconductivity, requires to bridging the quantum and classical worlds. This monumental challenge has so far only been achieved for systems close to their thermodynamical equilibrium. Here we follow in real time the ultrafast dynamics of the macroscale magnetic order parameter in the Heisenberg antiferromagnet KNiF 3 triggered by the impulsive optical generation of spin excitations with the shortest possible nanometre wavelength and femtosecond period. Our magneto-optical pump-probe experiments also demonstrate the coherent manipulation of the phase and amplitude of these femtosecond nanomagnons, whose frequencies are defined by the exchange energy. These findings open up opportunities for fundamental research on the role of short-wavelength spin excitations in magnetism and strongly correlated materials; they also suggest that nanospintronics and nanomagnonics can employ coherently controllable spin waves with frequencies in the 20 THz domain

Detection of solar-like oscillations in relics of the Milky Way: asteroseismology of K giants in M4 using data from the NASA K2 mission

Asteroseismic constraints on K giants make it possible to infer radii, masses and ages of tens of thousands of field stars. Tests against independent estimates of these properties are however scarce, especially in the metal-poor regime. Here, we report the detection of solar-like oscillations in 8 stars belonging to the red-giant branch and red-horizontal branch of the globular cluster M4. The detections were made in photometric observations from the K2 Mission during its Campaign 2. Making use of independent constraints on the distance, we estimate masses of the 8 stars by utilising different combinations of seismic and non-seismic inputs. When introducing a correction to the Delta nu scaling relation as suggested by stellar models, for RGB stars we find excellent agreement with the expected masses from isochrone fitting, and with a distance modulus derived using independent methods. The offset with respect to independent masses is lower, or comparable with, the uncertainties on the average RGB mass (4-10%, depending on the combination of constraints used). Our results lend confidence to asteroseismic masses in the metal poor regime. We note that a larger sample will be needed to allow more stringent tests to be made of systematic uncertainties in all the observables (both seismic and non-seismic), and to explore the properties of RHB stars, and of different populations in the cluster.Comment: 6 pages, 3 figures, accepted for publication in MNRA

Kepler red-clump stars in the field and in open clusters: Constraints on core mixing

Convective mixing in helium-core-burning (HeCB) stars is one of the outstanding issues in stellar modelling. The precise asteroseismic measurements of gravity-mode period spacing (&dela;σ1) have opened the door to detailed studies of the near-core structure of such stars, which had not been possible before. Here, we provide stringent tests of various core-mixing scenarios against the largely unbiased population of red-clump stars belonging to the old-open clusters monitored by Kepler, and by coupling the updated precise inference on &dela;σ1 in thousands of field stars with spectroscopic constraints. We find that models with moderate overshooting successfully reproduce the range observed of &dela;σ1 in clusters. In particular, we show that there is no evidence for the need to extend the size of the adiabatically stratified core, at least at the beginning of the HeCB phase. This conclusion is based primarily on ensemble studies of &dela;σ1 as a function of mass and metallicity. While &dela;σ1 shows no appreciable dependence on the mass, we have found a clear dependence of &dela;σ1 on metallicity, which is also supported by predictions from models